Molecularly Imprinted Polymers Adsorption Research Articles

Molecularly imprinted polymers (MIPs) as efficient catalytic tools for the oxidative degradation of 4-nonylphenol and its by-products.

Water pollution is a current global concern caused by emerging pollutants like nonylphenol (NP). This endocrine disruptor cannot be efficiently removed with traditional wastewater treatment plants (WTPs). Therefore, this work aimed to evaluate the adsorption influence of molecularly imprinted polymers (MIPs) on the oxidative degradation (ozone and ultraviolet irradiations) of 4-nonylphenol (4-NP) and its by-products as a coadjuvant in WTPs. MIPs were synthesized and characterized; the effect of the degradation rate under system operating conditions was studied by Box-Behnken response surface design of experiments. The variables evaluated were 4-NP concentration, ozone exposure time, pH, and MIP amount. Results show that the MIPs synthesized by co-precipitation and bulk polymerizations obtained the highest retention rates (> 90%). The maximum adsorption capacities for 4-NP were 201.1mg L-1 and 500mg L-1, respectively. The degradation percentages under O3 and UV conditions reached 98-100% at 120s of exposure at different pHs. The degradation products of 4-NP were compounds with carboxylic and ketonic acids, and the MIP adsorption was between 50 and 60%. Our results present the first application of MIPs in oxidation processes for 4-NP, representing starting points for the use of highly selective materials to identify and remove emerging pollutants and their degradation by-products in environmental matrices.

Synthesis of Molecularly Imprinted Polymers using Methacrylic Acid and Ethylene Glycol Dimethacrylate by Precipitation Polymerization Method

The synthesis of molecularly imprinted polymers (MIPs) was carried out by using methacrylic acid as a monomer, ethylene glycol dimethacrylate as a crosslink and dibutyl phthalate as a mold through the precipitation polymerization method. The MIP was characterized with FTIR, surface area analyzer, SEM-EDS and ultraviolet-visible spectrophotometer. The MIP adsorption ability test variables for dibutyl phthalate were time and concentration. The FTIR indicates that the functional groups –OH, –C=O and –C=C contribute to the formation of MIP and the SEM-EDS analysis showed that the prepared MIP resembles as beads. The MIP’s ability to adsorb dibutyl phthalate is better than NIP and the optimum time to adsorb dibutyl phthalate is 60 min.

Synthesis and Characterization of Molecularly Imprinted Polymers of Di-(2-Ethylhexyl) Phthalate Using The Precipitation Polymerization Method

Molecularly Imprinted Polymers (MIP) is a synthetic functional material that can recognize target molecules selectively. This study aims to synthesize and characterize MIP and its performance by precipitation polymerization method using methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), and di-(2-Ethylhexyl) phthalate (DEHP). Characterization of MIP was conducted by FTIR, SEM-EDS, SAA, and UV-Vis spectrophotometer. The effect of concentration and time on MIP adsorption ability against DEHP was also determined. SEM shows that MIP_DEHP_MAA-co-EGDMA surface morphology is arranged from more uniform, less tight, and more fine granules than NIP_MAA-co-EGDMA. FTIR characterization of MIP and NIP (Non-Imprinted Polymers) shows absorption bands of functional groups were –OH, C-H, C=O, and –C=C. SAA characterization shows MIP surface area is 137.660 m2/g, total pore volume 0.1555 cc/g, and an average pore radius 22.59 A that indicates as mesopore material. MIP_DEHP_MAA-co-EGDMA (AE) adsorbed DEHP better than NIP_MAA-co-EGDMA. The difference value of the adsorbed DEHP (qe) was 0.212 mg/g

Synthesis and characterization of stigmasterol imprinted polymers with precipitation polymerization method

Molecularly imprinted polymers (MIP) are porous materials that have an active binding site and can recognize specific target molecules. MIP synthesis was carried out by precipitation polymerization method using toluene as a porogen solvent and stigmasterol molecule as a template molecule. The synthesized NIP and MIP were characterized using FTIR and SEM-EDS. The ability of MIP adsorption on Stigmasterol was determined by concentration measurements using UV-Vis. The results of the characterization using FTIR showed that the functional groups that influence the formation of NIP and MIP are -OH, -CH, C=C, and -C=O. Characterization using SEM shows that the surface morphology of MIP is rougher than NIP. Characterization using EDS showed that there was a decrease in mass% by 2.54% and C% atom by 2.08% in MIP after extracting the Stigmasterol molecule. The ability of MIP adsorption on stigmasterol was 0.204 mg/g, while the ability of NIP adsorption on stigmasterol was 0.040 mg / g. The ability of MIP adsorption to stigmasterol molecules is better than NIP. Therefore, MIP can be used as an adsorbent to adsorb stigmasterol in sample extracts.

Molecularly imprinted dispersive solid-phase extraction coupled with high-performance liquid chromatography for the determination of pyraclostrobin in ginseng

Determination of pyraclostrobin in ginseng samples by molecularly imprinted dispersive solid-phase extraction (MIDSPE) coupled with high-performance liquid chromatography (HPLC) method was developed. Molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization using pyraclostrobin as template, methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) and azobisisobutyronitrile (AIBN) as cross-linker and initiator, respectively. The mixture of butanone (MEK) and n-heptane (7:3, V:V) was used as solvent and porogen. The microspheres were characterized by laser particle size analyzer, scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). Binding experiments showed high binding capacity of polymers, and that the maximum adsorption of MIPs and NIPs to pyraclostrobin was 73.01 mg g−1 and 59.14 mg g−1. Selective adsorption experiments verified that polymers had specific and selective recognition site for pyraclostrobin. Comparing MIPs with C18, the recoveries of pyraclostrobin from blank ginseng samples spiked at 0.05, 0.1, and 1.0 mg kg−1 ranged between 77.6% and 93.5% with the standard deviation of 2.18–6.07 and the relative standard deviations (RSDs) between 2.47 and 6.99% (n = 5). The recoveries of pyraclostrobin that used C18 as sorbent were found to be 53.04–63.86% with the standard deviation of 1.13–2.83 and the relative standard deviations of 1.07–4.99%. The data indicated that the method for the analysis of the pyraclostrobin in ginseng samples can achieve good recoveries, repeatability and reproducibility. The linear regression equation was calculated as y = 2.09935e−006x + 0.0176235 (R2 = 0.998656). The limit of detection (LOD, S/N = 3) was 0.01 mg kg−1. The confidence interval for the slope at the 95% confidence level was [356084.1828, 899542.8563], and the confidence interval for the intercept was [− 755349.2710, 72645.0856]. The MIDSPE-HPLC method showed specific selective separation and enrichment of trace pyraclostrobin in ginseng samples. The raw samples were tested and results were all below the maximum Residue Limit (MRL) 0.1 mg kg−1 in the European Union.

Exploring Matrix Effects on Binding Properties and Characterization of Cotinine Molecularly Imprinted Polymer on Paper-Based Scaffold

Commercially available sorbent materials for solid-phase extraction are widely used in analytical laboratories. However, non-selective binding is a major obstacle for sample analysis. To overcome this problem, molecularly imprinted polymers (MIPs) were used as selective adsorbent materials prior to determining target analysts. In this study, the use of non-covalent molecularly imprinted polymers (MIPs) for cotinine adsorption on a paper-based scaffold was studied. Fiberglass paper was used as a paper scaffold for cotinine-selective MIP adsorption with the use of 0.5% agarose gel. The effects of salt, pH, sample matrix, and solvent on the cotinine adsorption and extraction process were investigated. Under optimal conditions, the adsorption isotherm of synthesized MIPs increased to 125.41 µg/g, whereas the maximum adsorption isotherm of non-imprinted polymers (NIPs) was stable at 42.86 µg/g. The ability of the MIP paper scaffold to absorb cotinine in water medium was approximately 1.8–2.8-fold higher than that of the NIP scaffold. From Scatchard analysis, two dissociation constants of MIPs were calculated to be 2.56 and 27.03 µM. Nicotine, myosmine, and N-nitrosonornicotine were used for selectivity testing, and the calculated selectivity factor of cotinine to nicotine, myosmine, and N-nitrosonornicotine was 1.56, 2.69, and 2.05, respectively. Overall, the MIP paper scaffold is promising for simple onsite sampling of cotinine and can be used to assess tobacco smoke exposure.

Molecularly imprinted polymers based on zeolite imidazolate framework-8 for selective removal of 2,4-dichlorophenoxyacetic acid

Novel molecularly imprinted polymers (MIPs) based on zeolite imidazolate framework-8 (ZIF-8) stabilized Pickering emulsions polymerization were successfully prepared for the selective identification and separation of 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solutions. Experimentally, ZIF-8 of particle size of about 100 nm was successfully synthesized, which can be used as a stabilizer in Pickering emulsion. And then, with 2,4-D as the template monomer, 4-vinylpyridine (4-VP) as the functional monomer, the hollow spherical polymer microspheres were formed via Pickering emulsions polymerization. At last, after the removal of ZIF-8 and template, MIPs were obtained, which were characterized by Fourier transmission infrared (FT-IR) spectrometry and scanning electron microscopy (SEM). Through experiments, the results showed that the adsorption capacity of MIPs and NIPs had a good correlation with Langmuir isothermal model and the kinetic adsorption of MIPs was well suitable for the pseudo-second order kinetic model. The maximum adsorption capacity of MIPs was 108.10 mg/g, while that of NIPs was 28.22 mg/g. The imprinting factor (IF) was about 3.83. And the optimal adsorption equilibrium time was 60 min. The selective and regeneration adsorption experiments showed that MIPs had a high specific selectivity and stability. Also, MIPs revealed good selectivity for 2,4-D in complex water samples. On the basis, it could be proved that ZIF-8 is an excellent alternate for the traditional stabilizers and sacrificial materials, providing a new idea for separation and analysis of harmful substances in water environment.

Molecularly imprinted polymers combined with membrane-protected solid-phase extraction to detect triazines in tea samples

Spherical molecularly imprinted polymers (MIPs) were prepared by emulsion polymerization. The isothermal adsorption and selective adsorption indicated that the MIPs obtained exhibit excellent specific recognition for the template (atrazine) and its analogues. The MIPs were encapsulated in a polypropylene microporous membrane to fabricate MIP adsorption packages for the direct extraction of triazines in uncentrifuged and unfiltered tea extracts. The extraction conditions affecting the extraction efficiency, including the type and volume of extraction solvent, the number of MIP adsorption packages, the surface area of the MIP adsorption packages, the mass of MIPs in the MIP adsorption packages, the extraction time, the eluting solvent, and the eluting volume, were optimized. Under the optimal extraction and high-performance liquid chromatography-tandem mass spectrometry conditions, the method exhibited excellent linearity in the range from 0.5 to 250 ng g-1, with R2 ≥ 0.9992. The detection limit of the method was 0.09-0.18 ng g-1. The intraday and interday relative standard deviations ranged from 3.1% to 7.5% and from 3.1% to 7.9%, respectively. The method was successfully used to detect triazines in five tea samples. At a spiking concentration of 2 ng g-1, satisfactory recoveries ranging from (81 ± 3)% to (104 ± 7)% were obtained. The membrane-protected solid-phase extraction method based on molecularly imprinted material is expected to be widely used to enrich triazines in complex samples. Graphical Abstract Schematic illustration of the MIPs combined with membrane-protected solid-phase extraction of triazines in tea sample.

Molecularly Imprinted Polymers Chitosan-Glutaraldehyde for Monosodium Glutamate

Chitosan has been used as a functional monomer in the synthesis of molecularly imprinted polymers (MIP) for monosodium glutamate (MSG). MIP is made from a mixture of 5 g chitosan, 50 mg glutaraldehyde and 2 g MSG, MIP is formed as flakes and beads. MIPs are identified by the FTIR spectrum, SEM image and their adsorption capabilities. MIP flakes and beads have no structural differences if they are based on FTIR or SEM spectra, but MIP adsorption capacity of beads higher than flakes. Adsorption capacity of MIP flakes is 548 mg/g and MIP beads 627 mg/g.

Analysis of Melamine in Milk Powder by CNT-MIP with Matrix Solid Phase Dispersion and LC-MS/MS

In this work, a simple and selective method based on matrix solid phase dispersion (MSPD) using molecularly imprinted polymers (MIPs) as sorbents was successfully developed for the determination of melamine (MEL) in milk powder. The MIPs have been prepared by surface imprinted polymerization method using carbon nanotube (CNT) as support, MEL as template molecule, γ-aminopropyltriethoxysilane as functional monomer, and tetraethyl orthosilicate as cross-linking agent. The MIPs were characterized by Fourier transform infrared spectrometer and scanning electron microscopy. At the same time, the adsorption isotherm, dynamic adsorption, and selective adsorption of MIPs to MEL were also studied. The prepared MIPs were used as dispersant of MSPD to extraction and separate MEL in milk powder. We optimized the extraction conditions as follows: the ratio of MIPs to sample was 2:3; the dispersion time was 10 min; washing solvent was 2.0 mL acetonitrile; and elution solvent was 4.0 mL ammonium methanol (5:95, v/v). Once the MSPD process was completed, the MEL extracted from milk powder was determined by LC-MS/MS. Under the optimal conditions, the limit of detection of MEL was 0.2 ng g−1. The relative standard deviations of intra-day and inter-day were obtained in the range of 0.4∼5.1 %. The satisfied recoveries of MEL were 92.5∼97.2 %. The MIP-MSPD method has some advantages, such as higher selectivity, lower cost of preparation, less time consuming and organic solvent consumption, simpler sample pretreatment procedure, and higher extraction recovery compared with those existing methods which were used for determination of MEL.

Preparation of Roxarsone Imprinted Polymers and Its Application to Solid Phase Extraction

Molecularly imprinted polymers(MIP) with high selectivity to roxarsone(ROX) were prepared using arsanilic acid(ASA) as dummy template,2-Vinylpyridine(2-VP) as monomer,ethylene glycol dimethacrylate(EGDMA) as cross-linker.The effects of porogen,monomer and cross-linker on the recognition capability of MIP were investigated.The optimal ratio of ASA,2-VP,EGDMA,methanol-acetonitrile(1 ∶ 1,V/V) and azobisisobutyronitrile was 1 mmol ∶ 4 mmol ∶ 20 mmol ∶ 6 mL ∶ 60 mg,respectively.The maximum adsorption of MIP to ROX was 0.93 mg/g.The optimal conditions of solid phase extraction of MIP as adsorptive material for selective extraction and enrichment of ROX were: conditioning with water and acetonitrile,loading ROX in acetonitrile,washing with water and methanol,and eluting with methanol-formic acid(95 ∶ 5,V/V).The recovery of ROX on MIP cartridge was above 95% and that on NIP cartridge was only 43.1%.The prepared MIP cartridge was applied to extract and enrich ROX in pond water,and the limit of detection of ROX was 0.05 mg/L.

The Effect on Adsorption Performance of Molecularly Imprinted Polymer Using the Different Functional Monomers

To prepare molecularly imprinted polymers (MIPs) with good recognition properties，the effect on the MIPs adsorption performance were investigated from the different functional monomers. The MIPs were synthesized by using andrographolide as template, and α-methyl acrylic acid (MAA), acrylamide (AM) and 1 - vinylimidazole were used as functional monomer. Before polymerization, the interaction between the template molecule and the two functional monomers was studied by UV spectrum. After polymerization the different adsorption properties of MIPs prepared by the three types of functional monomers were compared by equilibrium binding. The results showed that the adsorption properties of the MIPs by 1-vinyl imidazole as functional monomer were similar to the MIPs by AM as functional, which the former is slightly higher than the latter and significantly higher than that of the one by MAA as functional monomer.

Binding assays with molecularly imprinted polymers—why do they work?

The design of homologous displacement ligand binding assays based on molecularly imprinted polymers (MIP) is discussed in terms of the MIP adsorption isotherm. It is shown that only MIPs having a binding isotherm with varying slope are suitable for the assay, but there is no need to interpret the isotherm in terms of site affinity and population. One can calculate the calibration plot of the binding assay from the isotherm and vice versa.